Developing Best Practice in Micropalaeontology: Examples From the Mid-Cretaceous of the Zagros Mountains

Abstract

Micropalaeontological studies can provide important information on how strata correlate, age calibration, palaeoenvironmental determination, palaeobiology, evolutionary relationships of the taxa being studied, palaeogeography, and the recognition of global or regional geological events in a local succession. However, the value of micropalaeontological studies is constrained by the accuracy with which taxa are identified, the accuracy of their age interpretation, and the use of up-to-date taxonomic concepts, supported by modern research literature. Best practice implies attention to these and other details, which we illustrate with reference to published research on larger benthic foraminifera (especially orbitolinids) from the mid-Cretaceous succession of the Zagros Mountains in the Middle East. It is demonstrated that whilst there are many excellent studies, a significant number could offer more value if they were to use precise, modern taxonomic concepts applied to well-illustrated and documented unequivocal material. Poorly founded age assignments and misidentifications can lead to confusion on assessment of true stratigraphic ranges and evolutionary patterns. Moreover, they can lead to miscorrelation and erroneous modelling of the subsurface in a hydrocarbon-rich region. Integrated studies of larger benthic foraminifera with other age-diagnostic fossil groups or chemostratigraphic methods would further enhance their utility. These recommendations are applicable to micropalaeontological studies on microfossils of any type and age, from any part of the world, but we hope will promote additional rigour in studies on the micropalaeontology of the Mesozoic and Cenozoic succession of the Zagros that still have much to impart.

Sequence Stratigraphy, Palaeogeography and Petroleum Plays of the Cenomanian – Turonian Succession of the Arabian Plate: An Updated Synthesis

“…The Nezzazatinella-Dicyclina biozone ofWynd, (1965) is recognized within wells from these fields suggesting a possible early Turonian age for the uppermost part of the Sarvak Formation (Rahimpour-Bonab et al, 2013;Omidvar et al, 2014). However, definitive proof of early Turonian Sarvak Formation in platform settings is lacking from the microfauna present (Schlagintweit and Simmons, 2022).…”

“…9, Ahwaz 355 well). It should be noted that unequivocal biostratigraphic evidence for a Turonian age for the uppermost Sarvak platform is lacking, although this is not the case in more open-marine facies of the Sarvak Formation (Sharp et al, 2010;Schlagintweit and Simmons, 2022). Zone 29 of Wynd, (1965) within the upper Sarvak platform (the Valvulammina-Dicyclina Assemblage Zone), was renamed the Moncharmontia apenninica -Nezzazatinella -Dicyclina Assemblage Zone by Omidvar et al (2014) with the observation that this is Turonian in age, mainly because of the presence of Moncharmontia apenninica.…”